Process and apparatus for making centrifugal concrete pipes



Feb. 26, 1924.; 1,485,142

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I J. C. MITCHELL PROCESS AND APPARATUS FOR MAKING CENTRIFUGAL CONCRETEPIPE 3S Filed April 28. 1922 7 Sheets-Sheet 6 A L I[HilllIIIIlllllllllllllllllllllllIlllllllll llllllllllllllllll il IIIIIIIlllllll I llllllll l Feb. 26, 1924. 1,485,142

J. c. MITCHELL PROCESS AND APPARATUS FOR MAKING CENTRIFUGAL CONCRETEPIPES Filed April 28. 1922 7 Sheets-Sheet awve'ntoz Patented Feb. 26,1924.

UNITED-STATES PATENT OFFICE.

JOHN C. mCHELL, OF E, NEW JERSEY, ASBIGNOB TO LOOK JOINT PIPE COKPAN'Y,01 Pm NEW JERSEY, A. CORPORATION 01 NEW. JERSEY.

PROCES ANDAPPABATUB 1'03 MAKING CENTRIIUGAL CONCRETE PIPES.

I Application filed April 28, 1922. Serial No. 557,188.

To all whom it may concern:

Be it known that I, JOHN C. MITCHELL, a citizenof the United States ofAmerica residing at East n e, in thecounty of 5 Essex and State. of NgwJerse have invented certain new and usefu Improvements in. Processes andAp aratus for Making Centrifugal Concrete ipes, of which the. followingis a full, clear, and exact 0 description.'

One of the most remarkable and excelptionally valuable contributions tohydrau 1c engineerin if it be properly made, is what is common y knownas centrifugal concrete pipe, or pipe composed of concrete molded m asuitable form centrifugally. Theoretically the production of such pipes,whether without or with the reinforcements required to give them thenecessary strength, is not a matter of much .difiiculty, but thepractical requirements of pipe lines for carrying water demand not onlyimperviousness to fluid under pressure, and great strength to resistboth external and internal stresses, 26 but a smoothness of interiorfinish which will not oppose too high a frictional resistance to theflow of the water or other fluid. Unless all of these properties bepresent to a very perfect degree, such pipes lose their advantages overcast iron or other forms of pipe that are equally available even if moreexpensive to produce.

Recognizing these requirements I have devoted much time and study to thesubject and as the result of many experiments and tests I have devisedan apparatus and a process for the manufacture of centrifugal concretepipes which form the subject of this application for Letters Patent 40and which produce such pipes more nearly ideal in character than anythat have come under my observation. Fora more ready understanding ofthis invention and the nature of the results which it yields, let

it be assumed that a form or tubular'mold' be mounted so as to becapable of archtively rapid rotation, and that a given quantity ofconcrete be introduced therein. By centrifugal force the concrete isthrown outwardly against the wall of the mold and may be assumed tospread in a layer of approximately uniform thickness -over such wall. In.a relatively short time the concrete solidifies and all of its li hterconstitutents coming to the inner sur ace of the tube, suchconstitutents comprisin 'once seen what has water froth, laitance, andthe lighter so id par ticles. Heretofore this has been practically theextent of the process carried out in the making of these ipes, but whenthe concrete has hardene or dried, the inner surface of the pipe isrough, uneven, and not of the same density as the remainder, and

this makes the pipes unsuitable for many purposes where the frictionalresistance to 6 internal flow is a factor in the ultimate purpose of thepipes. This objection might, m a measure, be removed, but only by meanswhich prohibitively increase the cost of the finished product; 7

It has been pro sed to smooth'ofi' the interior surface 0 these pipesbefore the cement has hardened by a scraper with a rlgid edge appliedthereto, but if the speed of rotat1on.o the pipe and the force due tomomentum be considered, it will be at been amply demonstrated inpractice that this is entirely impracticable.

To avoid this I remove by a wiping action 30 the laitance and otherobjectional matter from the surface of the pipe during the moldingprocess, thus leavmg a surface of pure concrete only, and over thiscleaned surface I then flow a small amount of neat cement, with orwithout sand and water or other suitable material to form a surfacecoating a fraction of an inch in thickness and before it has fully setor before the rotation of the mold is stopped I clean this surface ofthe water and lighter impuritieswhich collect on it by means of abrushor some soft body that will clean and polish the surface. ipes madein this wa are of very high grade, possessing not on y the valuableproperties of centrifugal concrete, but having a very hard smoothinterior surface which opposes only a negligible frictional resistanceto water flowing over it.

To practically accomplish all the steps 1 necessary in carrying out mynovel process a somewhat elaborate apparatus is desirable, though in allparticulars not essential, and in the drawings hereto annexed I haveillustrated such apparatus in full detail. To these drawings I'nowrefer.

Fig. 1 is a view partly in elevation and partly in section of theprincipal devices necessary in carrying out the process.

Fig. 2 is a similar view of means for 0 v the second or other mixing anddelivering concrete to the apparatusf Fig. 3 is a topflplan view of acomplete apparatus design to carry out the invention.

Fig. 4 is 9. art vertical section and part elevation of t e portions ofthe apparatus for delivering the mixed concrete.

Fig. 5 is an end view in elevation of the molds and means of su perttherefor.

Fig. 6 is an enlarged lon itudinal section of a mold containing a Hingof concrete, showing also the means for cleaning a the interior surfaceof the tube.

Fig. 7 is a longitudinal section of the mold and container whichintroduces the concrete, in position in the mold.

Fig. 8 is a transverse section of the mold with the container in placetherein.

Figs. 9, 10 and 11 are details of molds showing the manner of formingthe joints.

Fig. 12 is an enlarged transverse section of the mold, its means ofsupport, and the cleaning device inserted therein.

Fig. 13 is an enlarged sectional detail of that part of the mold withwhich the steadying rollers engage.

Fig. 14 is an enlarged sectional view of a concrete tube in the moldshowing the finishing or polishing brush aplied thereto; and V Fig. 15is a similar view showing the means for introducing the layer of neatcement of finishing coat to the interior of the concrete tube.

In the practical carrying out of the invention I employ a duplexarrangement of molds and other devices whereby while one mold isrotating to ermit the introduced concrete to solidify, t e concrete foranother mold may be mixed and got ready so that mold may be filled assoon as the first is removed with its set filling, and so on without anyinterruption in the process. As each mold, with its accessories, is,however, the counter-part of another the description will be confined toone only.

For the proper installation and support of the essential parts of thedevice I employ a strong framework 1. In the forward part of this frameare two grooved pulleys 2, 3, driven by suitable power and carryingendless belts of wire rope 4, or the like, which surround groovedpulleys or projections 5 on the mold 6. The mold is a plain cylinder intwo or more parts which, as shown in Fig. 11, have longitudinal flanges7, which are clamped by bolts to complete the cylinder and which may bereadily taken apart for the removal of a set and hardened tube.

The annular raised portions 5, which constitute the pulleys, are securedto the mold by rivets 8, which secure flanges 9 on said either at thepoint 0 contact or in their bearings, are mounted on the frame onopposits sides of the mold, and in order to prevent undue side sway orand thrust, enter the ggooves in the pulleys 5 over the endless lts, asshown in Figs. 12 and 13.

In order that the wheels 10 should most effectively exert their allottedfunction they are provided with rubber tires or rims, but under allordinary circumstances the degree to which they should yield is veryslight.

I At the rear of the frame is arranged a concrete mixer 11, and a trough12, into which charges of mixed concrete in proper amount are dumped. Ontracks 13 carried by the frame is suspended a'cradle 14, carrying acounterweighted cylinder or receptacle 15, of a length substantiallyequal, beyond said cradle, to that of the mold. This cylinder orreceptacle, shown in detail in Fig. 7 is mounte concentrically with themold 6 and in position to be moved into the same b means of the cradle14. Normally it lies a on ide the trough 12, from which it is fills withthe exact amount of concrete required to form a pipe section, and it isso supported that it may be rotated about its axls by means of'a handwheel 16, Fig. 1, which is connected to the cylinder by a belt andpulleys or by any other well known means. I

The cylinder 15, as shown in Figs. a and 8, contains a longitudinal slotthrough which it is filled by any suitable funnelshaped appliance 17,Fig. 4, and until it is forced forward into the mold it occupies theposition shown in this figure, with the slot at the top. Through thecylinder 15 extends a shaft 18 carrying arms or blades 19, constitutinga stirrer which shaft may be rotated, whenever desired, by a handle 20.

To mold a pipe section by means of this apparatus the exact predterminedamount of concrete required to form it is mixed and run into thecylinder 15. The mold, in which the reinforcements 21 are placed, andhaving placed over its ends flanges 22, the internal diameters of whichare less than that of the completed pipe section, is swung in theendless belts 4 and started in rotation.

The cylinder 15 is then forced forward into the mold and by the handwheel 16 turned to gradually deliver its contents into the mold. Whilethis operation is going on the shaft 18 is rotated whereby the concreteis delivered evenly and properly through the slot in the cylinder. Bycentrifugal force the concrete is thrown out against the inner wall ofthe mold, and after the entire contents of the cylinder 15 have beendelivered the latter is withdrawn to its first or'normal position. j

Under ordinaryconditions the concrete will have solidified sufiicientlyin the rotating mold in about fifteen or twenty minutes, when a trough23 is passed into or through the mold with the pipe section "formedtherein, this tron h being of snfiicient length to extend entire ythrough the same and to rest on fixed supports by which it is supportedtherein about the relative ositlon shown in Figs. 12 and 14. 1s troughhas rounded bars 24 along its edges, one of which serves as a guide fora properly shaped support 25, Figs. 6 and 12, attached to a long rod 26carrying a stiff wire brush or similar wiper 27. TlllS rod is introducedinto the tube and forced back and forth with the brush or wiper lyingagainst the inner surface of the tube, with the result that the .waterand all the soft material concentrated on the said surface is thrown offinto the ti'ough 23, leaving the solid concrete surface c ean.

The next step is to fill a lon trough 28, Fig. 15, with neat cement orot er material for finishing coat, and pass this into the tube,utilizing the side bar of the trough 23 as a guide as shown. When thistrough is fully inserted, it is tipped, as shown in dotted lines, todeliver its contents onto the inner surface of the concrete tube. By thesame centrifugal action this cement is flowed evenly over the surface ofthe tube to form acoating a fraction of an inch in thickness, whichquickly solidifies. As soon as it has sufiiciently set, the trough 28having been withdrawn, a softer brush 29, with a su port 30, isintroduced and guided by the si e rod of the trough 23. This brush maybe of any width desired. Its function is merely to remove the water fromthe surface of the cement or any light impurities that may collectthere, and to impart to the solid cement surface a smooth finish. Ifthis finish is not snfliciently smooth another soft brush 31 may bepassed over the inner surface along the other side bar of the trough 23,asshown in Fig. 15.

After having gone through with the above described operations, thetrough 23 is withdrawn, the mold stopped and removed to give place toanother and empty mold, and laid aside fora suflicient time to permitthe concrete tube to thoroughly harden, when the mold is removed fromthe tube.

The 'unessential details of the apparatus I have not deemed it necessaryto describe in any detail. These are the means. for imparting rotationto the parts requiring such movement; the means for stopping andstarting the various parts in rotation; the

means for removing or replacing the molds;

the means for supporting the trough in the vmaintained in their tube andthe like, as all of these are matters well'within the knowledge of anone skilled in this art. The features whic tial to and characteristic ofmy new process,

however, and .by whatever means they may.

be carried out, are as follows:

1. The removal of water and all deleterious matter from the interiorsurface of the concrete tube by a wiping as distinguished guish theapparatus which I have devised r carryin out this process are asfollows:

N o fixed arings for or under the molds are emplo ed but. the latter areslung in endless be ts and rotated thereby, and are proper position bysteadying wheels.

It has been found that the interior of centrifugally formed concrete pies cannot be smoothed, trued or finished by any rigid body appliedthereto and which is designed to remove any part of the surface by whatI now term a scraping or cutting action. I I have found that Whatevermeans be em-' ployed for truing or finishing these surfaces ut becapable of yielding in the direction of rotation of the mold so as toexert what I term a wiping action is suitable. The distinction is thesame in principle as plough or tool cuttin on the one hand and sweepingon the ot er, and it is only by sweeping or wipin that the proper anddesired ortions of t e surface can be removed to eave a substantiallyeven or true surface. The failure of previous a paratus for this purposehas been lar ely 16 mans radical defect. It is impossilile to preservefor any appreciable time any ordinary form of stationary bearing aboutamachine of this nature. No matter how carefully such bearings may beprotected, they are worn out in a very short time by the grinding actionof the fine cement which inevitably finds its way into them. Bysuspending my molds in rotating slings I avoid this objection entirely,and I have found that my apparatus remains unimpaired for months, wherethe ordinary bearings last only for hours.

It is highly essential that a trough be used to catch and retain theremoved materialare essen from the inner surface of the concrete tube,

otherwise it would be most diflicult to secure the proper finish of thetubes.

It is equally important that when the'concrete or cement is delivered tothe mold or wise it is extremely diflicult to obtain tubes of uniformthickness. The devices which I I use for this purpose I have found to beentirely successful.

Having now descrlbed my invention, what I claim is:

1.. In the process of making centrifugally molded concrete pipes, thesteps herein described of depositing concrete in a rotating mold andremoving the 'laitance and other objectionable matter from the interiorsurface of the pipe body yielding 1n the direction of rotation of themold and while said mold is still in rotation.

:2. In the process of making centrifugally molded concretepipes, thesteps herein described of depositing the concrete in a ro-' tating mold,removing the laitance and other objectionable matter from the interiorsurface of the (pipe by a resilient wiper, trailing in the irection ofthe rotation of the mold and while the latter is still in rotation,

and then de ositing in the pipe while still rotating a t in interiorcoating of fine ce-.

ment.

3. In the process of making centrifugally molded concrete pipes thesteps-which consist in forming in a centrifugal mold a concrete pipesection, wiping the inner surface to clean and true the same, depositingon said surface while still rotating a material such as neat cement toform a finishin coating, and smoothing the surface of suc 1 coat.-

ing by a wiping or brushing action while the pipe is still in rotation.

4. The combination with a rotary mold for the manufacture ofcentrifugallv molded concrete pipes, of overhead pulleys in fixedbearings, endless belts running over concrete pipes, of an elongatedcylindrical receptacle for concrete, revoluble about its for receivingand delivlonlgitudinal axis and movable concentriresilient wiper, aapted to trail in the direction of rotat on of the mold over the innersurface of. the pipe and to thereby'remove the laltance and otherobjectionable matter by the wiping action of 1k therefrom, and adaptedto slide along the edge of said trough as a guide. v

' 7. Thecombination with a rotary mold .for the manufacture ofcentrifugal concrete pipes, of overhead pulleys in fixedbearings,endless belts running over the same, pulleys on the mold slung in theendless belts, and

yielding steadyin'g wheels on op osite sides of lilac mold engaging withthe pn eye on the mo Y 8. The combination with" a rotary mold for themanufacture of centrifugal concrete pipes, of an-elongated'cylindricalreceptacle capable of rotation on its axis, movable conccntrically intoand out of the mold, and

provided with a lon 'tudinal slot and a stirrer mounted in sai cylinderand capable of being turned therein to assist in the even delivery ofits contents when within the mold. v

9. The combination witha machine for making centrifugal concrete pipe,of an elongated trou h adaptedto be passed into and through t e pipewhen formed, a supplemental tilting. trough for the material of afinishing coating, adapted to travel along the edge of the main troughand 'be guided thereby into the :pipe.

10. The combination .with a machine for making centrifugal concretepipe, of an elongated trough adapted to be passed-into and through'thepipe when formed, of a brush adapted to be forced back and forth alongthe edge of said trough in contact with the inner surface of the tilbefor cleaning and smoothing thesame.

In testimony whereof I hereto aflix my signature,

= JOHN C. MITCHELL.

